Thanks all

Yes, they are a bit boring to paint, and I was dreading doing them too, which is why I decided to make them interestingly rusty - historically accurate or not

Excellent addition to your canon
You missed your vocation in Vaudeville Chris

The weathered iron is superb, how did you do it?
It's really dead simple.
The iron parts are painted with a mix of black and burnt sienna for a very dark 'russeted' red-brown.
Then once dried, a very watered down wash (like almost all water and just the merest bit of paint) mixing burnt sienna and Vallejo bright orange... Slosh it on and let it pool around the nuts and bolts. if it doesn't pool in the right places, gently encourage it with the tip of a fine paintbrush...
Once dried, it leaves a slightly rusty looking film over all the metal parts, and a convincing rustiness around the joints... If it's not enough, just repeat the wash until you build up the depth of colour you require, increasing the amount of orange to taste, depending on how blatant you want your rust...